Magnetic field sensor with a hall element

ABSTRACT

A symmetrical vertical Hall element comprises a well of a first conductivity type that is embedded in a substrate of a second conductivity type and which is contacted by four contacts serving as current and voltage contacts. From the electrical point of view, such a Hall element with four contacts can be regarded as a resistance bridge formed by four resistors R 1  to R 4  of the Hall element. From the electrical point of view, the Hall element is then regarded as ideal when the four resistors R 1  to R 4  have the same value. The invention suggests a series of measures in order to electrically balance the resistance bridge. A first measure exists in providing at least one additional resistor. A second measure exists in locally increasing or reducing the electrical conductivity of the well. A third measure exists in providing two Hall elements that are electrically connected in parallel in such a way that their Hall voltages are equidirectional and their offset voltages are largely compensated.

CROSS REFERENCE TO RELATED APPLICATION

The present application is related to and claims priority of the PCTapplication number PCT/CH02/00497 of Sentron AG entitled Magnetic fieldsensor with a Hall element, filed on Sep. 10, 2002, the disclosure ofwhich is incorporated by reference.

FIELD OF THE INVENTION

The invention concerns a magnetic field sensor with a symmetricalvertical Hall element of the type.

For years now, magnetic field sensors that are based on a Hall elementhave been produced in large numbers and are used in industry, inhousehold equipment and in vehicle manufacture as position switches orfor position measurement. Hall elements that are manufactured withcustomary IC technology have all the advantages of this technology inparticular the high reproducibility of their magnetic and electricalcharacteristics at comparatively low cost. So-called horizontal Hallelements are used for measuring the components of the magnetic fieldthat run vertically to the chip surface, while so-called vertical Hallelements are used for measuring the components of the magnetic fieldthat run parallel to the chip surface.

A conventional Hall element has four contacts, namely two currentcontacts for the supply and discharge of a current flowing through theHall element and two voltage contacts for tapping the Hall voltageproduced by the component of the magnetic field to be measured. Afundamental problem of the Hall elements is that a voltage, theso-called offset voltage, is present between the two voltage contactseven when no magnetic field is present. Two techniques have beendeveloped in order to reduce the offset voltage. With one technique thatis applied with horizontal Hall elements, two horizontal Hall elementsare used whereby the two currents that flow through the two Hallelements form an angle of 90°. With the other technique known from U.S.Pat. No. 4,037,150 that is suitable for symmetrical Hall elements thatare electrically invariant in relation to a reversal of the current andvoltage contacts, the current and voltage contacts are electricallycommutated. In accordance with U.S. Pat. No. 5,057,890, this techniquethat was developed for horizontal Hall elements can also be used forvertical Hall elements with which the position and size of the currentand voltage contacts have been calculated by means of conformal mappingof a symmetrical horizontal Hall element.

The present invention concerns symmetrical vertical Hall elements, theseare Hall elements with which four contacts, namely two inner and twoouter contacts, are arranged along a line. Typically, the two innercontacts are the same size and the two outer contacts are the same size.The current always flows from one inner contact to the not neighbouringouter contact or vice versa. With these symmetrical vertical Hallelements, because of their geometrical symmetry, the current and voltagecontacts can be reversed, that means electrically commutated, withoutchanging the electrical and magnetic characteristics of the Hallelement.

Symmetrical vertical Hall elements are known from the above quoted U.S.Pat. No. 5,057,890 and from the article “A Symmetrical VerticalHall-Effect Device” that was published in the magazine Sensors and theyhave only been manufactured with a special technology that does notallow the integration of electronic switching elements as well as Hallelements onto the same semiconductor chip.

A vertical Hall element with bipolar technology is known from U.S. Pat.No. 5,572,058. With this technology, the Hall element is insulated fromthe substrate so that, apart from the Hall element, electronic elementscan also be integrated onto the same semiconductor chip. However, thisvertical Hall element that has five contacts arranged along a straightline, namely a central contact and two outer contacts that serve ascurrent contacts and two voltage contacts that are arranged between thecentral contact and one of the outer contacts, does not belong to thegroup of symmetrical vertical Hall elements because the electricalcharacteristics of the Hall element change on a reversal of the currentand voltage contacts.

The object of the invention is to develop a symmetrical vertical Hallelement that can be realised in an N-type well of a CMOS technology withwhich, in terms of potential, the two voltage contacts lie roughly inthe middle between the potentials of the two current contacts and withwhich the offset voltage is as low as possible.

With this object, on the one hand there is the problem that the lengthsof the current and voltage contacts calculated by means of conformalmapping are less than the minimum dimensions that are possible with thetechnology. The reason is that the depth of the N-type well is very lowin comparison to the distance between the outer edges of the outercontacts. If the current and voltage contacts are enlarged in relationto the calculated ideal values corresponding to the minimum requirementsof the technology, then, in terms of potential, the two voltage contactsno longer lie in the middle between the potentials of the two currentcontacts, the offset voltage becomes comparatively very high and thesensitivity is greatly reduced. When, in terms of potential, the twovoltage contacts no longer lie in the middle between the potentials ofthe two current contacts, then this means that the commutation of thecurrent and voltage contacts can no longer be meaningfully applied.Furthermore, the doping of the N-type well is not homogenous. This hasthe result that firstly the largest part of the current flows directlyunderneath the surface of the Hall element, typically in a layer of onlyone to two micrometers thickness even when the N-type well has adiffusion depth of several micrometers and, secondly the theory ofconformal mapping is no longer applicable.

The invention starts with a symmetrical vertical Hall element with fourcontacts, namely two inner and two outer contacts that are arrangedalong a line on the surface of a semiconductor chip. The two innercontacts are preferably of the same width and the two outer contacts arepreferably of the same width whereby the width of the contacts ismeasured in the direction of the straight line.

The symmetrical vertical Hall element comprises a well of a firstconductivity type that is embedded in a substrate of a secondconductivity type. The four contacts contact the well. From theelectrical point of view, such a Hall element with four contacts can beregarded as a resistance bridge formed by four resistors R₁ to R₄ of theHall element. When operating the Hall element as a magnetic fieldsensor, a current always flows between two contacts that are notadjacent. From the electrical point of view, the Hall element is thenregarded as being ideal when the four resistors R₁ to R₄ have the samevalue. In this case, on supplying the Hall element via two currentcontacts, the contacts serving as voltage contacts are located on thesame electrical potential namely the potential of half of the supplyvoltage. Furthermore the voltage between the voltage contacts, theso-called offset voltage, is then equal to zero, ie, the offset voltagedisappears. The same is also valid when the roles of the current andvoltage contacts are reversed.

In accordance with the invention it is suggested to arrange the fourcontacts of the Hall element in such a way that three of the fourresistors R₁ to R₃ for geometrical reasons are almost the same size. Thefourth resistor R₄, namely the electrical resistance between the twoouter contacts, is larger than the other resistors R₁, R₂ and R₃. Inorder to balance the resistance bridge, in accordance with the inventionit is furthermore suggested to arrange another resistor R₅ parallel toresistor R₄ the value of which is defined so that approximatelyR₁=R₂=R₃=R₄||R₅ is valid. The resistor R₅ is, for example, an externalresistor. Preferably however the resistor R₅ is embedded in the well ofthe Hall element or is realised as a separate N-type well. In the firstcase, the resistor has at least one contact that contacts the well ofthe Hall element and is arranged next to one of the two outer contactson the side facing the edge of the well of the Hall element. In thiscase, the advantage exists in that the resistor R₅ has the sametemperature coefficient as the resistors R₁, R₂, R₃ and R₄ so that theresistance bridge remains balanced even with variations in temperature.

Another possibility of electrically balancing the resistance bridgeexists in providing both at least one electrode electrically insulatedfrom the well whereby the at least one electrode is arranged between twocontacts. The at least one electrode serves to locally increase orreduce the electrical conductivity of the well in the area underneaththe electrode.

A further possibility of electrically balancing the resistance bridgeexists in locally increasing or reducing the electrical conductivity ofthe well in the area between two contacts by means of local implantationof additional or fewer ions.

A further possibility of electrically balancing the resistance bridgeexists in using a magnetic field sensor with a first Hall element and asecond Hall element that each have two inner and two outer contactsarranged along a straight line whereby preferably the two inner contactsare the same width and whereby preferably the two outer contacts are thesame width, whereby the straight lines of the two Hall elements runparallel and whereby the contacts of the two Hall elements are wired viaconductor paths in such a way that their Hall voltages areequidirectional and their offset voltages are largely compensated sothat the total resulting offset voltage almost vanishes.

Various embodiments of the invention are explained in more detail belowbased on the drawings. The figures shown in the drawings are not toscale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-section of a symmetrical vertical Hall element,

FIG. 2 shows a plan view of the symmetrical vertical Hall element,

FIG. 3 shows an equivalent circuit diagram for the symmetrical verticalHall element,

FIG. 4 shows a symmetrical vertical Hall element with an integratedresistor,

FIG. 5 shows a symmetrical vertical Hall element with two integratedresistors,

FIG. 6 shows a symmetrical vertical Hall element with additionalelectrodes,

FIG. 7 shows a mask that, on the implantation of ions, is used for theformation of an N-type well, and

FIGS. 8, 9 show two anti-parallel connected Hall elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 show a cross-section and a plan view of a symmetricalvertical Hall element 1. The Hall element 1 manufactured with a CMOStechnology preferably comprises a well 2 of a first conductivity typethat is embedded in a substrate 3 made of silicon of a secondconductivity type. The Hall element 1 has four contacts 4-7 on thesurface, namely two inner contacts 5 and 6 as well as two outer contacts4 and 7. The contacts 4-7 are arranged along a straight line 8 (FIG. 2).Preferably the two inner contacts 5 and 6 are the same width as seenalong the straight line 8 and the two outer contacts 4 and 7 are thesame width. The position and size of the well 2 and the contacts 4-7 arethen symmetrical in relation to a plane 9 that runs perpendicularly tothe straight line 8 and in the middle between the two inner contacts 5and 6. (For technological reasons it makes sense to make the two innercontacts 5 and 6 the same width and the two outer contacts 4 and 7 thesame width but is not absolutely necessary.)

Because with silicon the mobility of the electrons is greater than themobility of the holes, it is advantageous when an N-type well and not aP-type well is used for the Hall element 1. A P-type well could be usedfor the Hall element 1 however the sensitivity of the magnetic fieldsensor would then be distinctly lower.

The depth t of the well 2 amounts typically to around 5 μm. Because thedoping of the well 2 is not homogenous but reduces exponentially withincreasing depth, the greatest part of the current flows underneath thesurface of the Hall element 1 in a thin layer of typically 1-2 μmthickness. The depth t_(eff) of the well 2 effective for the electricaland magnetic characteristics of the Hall element 1 therefore onlyamounts to around 1-2 μm. The length L of the Hall element 1 is given bythe length of the well 2. Essentially, it corresponds to the distancebetween the outer edges 10 and 11 of the outer contacts 4 and 7. Thelength L is large in comparison to the depth t or to the effective deptht_(eff). The electrical characteristics of the Hall element 1 can berepresented by a resistance bridge formed from four resistors R₁ to R₄.For ease of understanding, in FIG. 1 the resistances prevailing betweentwo contacts are each presented by a resistor symbol R₁ to R₄ and a linethat connects the contacts corresponding to the resistor.

FIG. 3 shows the electrical circuit diagram of the resistance bridgeformed by the four resistors R₁ to R₄ of the Hall element 1. Onoperation of the Hall element 1 as a magnetic field sensor, a currentalways flows between two contacts that are not adjacent, for examplebetween the contacts 4 and 6 or between the contacts 5 and 7. Form theelectrical point of view, the Hall element 1 is then regarded as idealwhen the four resistors R₁ to R₄ have the same value. In this case, onsupplying the Hall element 1 via the contacts 4 and 6, the contacts 5and 7 serving as voltage contacts both have the same electricalpotential, namely the potential of half the supply voltage. Furthermore,the voltage between the voltage contacts is then equal to zero, ie, theoffset voltage vanishes. The same is valid when the Hall element 1 issupplied via the contacts 5 and 7 and the contacts 4 and 6 serve asvoltage contacts.

For geometrical reasons, the resistors R₁ and R₃ are the same size. Theresistor R₂ can be altered by increasing or reducing the distancebetween the inner contacts 5 and 6. By means of appropriate selection ofthe position and size of the contacts 4-7, one can therefore achievethat approximately R₁=R₂=R₃ is valid. In addition, it is valid that theresistor R₄ is larger than the other resistors R₁, R₂ and R₃. In orderto balance the resistance bridge, in accordance with the invention it issuggested to arrange a further resistor R₅ parallel to the resistor R₄the value of which is defined so that approximately R₁=R₂=R₃=R₄||R₅ isvalid. The resistor R₅ is for example an external resistor. However theresistor R₅ is preferably embedded in the N-type well 2 of the Hallelement 1 or is realised as a separate N-type well. In this case, theadvantage lies in that the resistor R₅ has the same temperaturecoefficient as the resistors R₁, R₂, R₃ and R₄ so that the resistancebridge remains balanced even with temperature variations.

FIGS. 4 and 5 show two examples with which the resistor R₅ is embeddedin the well 2 of the Hall element 1. For ease of understanding, theresistances prevailing between two contacts are again represented by aresistor symbol and a line connecting the corresponding contacts. Withthe example according to FIG. 4, a further contact 12 is arranged nextto the contact 4 that is connected to the contact 7 by a purelyschematically represented conductor path 13. With the example accordingto FIG. 5, a further contact 12 is arranged next to the contact 4 and afurther contact 14 is arranged next to the contact 7 whereby the twoadditional contacts 12 and 14 are again connected by an onlyschematically represented conductor path 13. With this example thereforethe resistor R₅ is realised not by means of one single resistor but bymeans of two resistors with the value 1/22R₅.

Limits are set on the miniaturisation of the Hall element in that atechnology dependent minimum distance has to be maintained between thetwo inner contacts 5 and 6. Today, this minimum distance lies in thearea of around 0.8 μm. The resistor R₂ can therefore not fall below acertain value predetermined by the technology used. In the following,further examples are explained as to how the resistors R₁ to R₃ can beincreased or reduced.

With the example according to FIG. 6 three electrodes 15-17 are arrangedbetween the contacts 4-7 that, for example, are realised out ofpolysilicon like the gate electrodes of a MOSFET. The electrodes 15-17are separated from the N-type well for example by means of a thin oxidelayer and therefore electrically insulated from the N-type well 2. Onoperation of the Hall element 1, each of the electrodes 15-17 is biasedwith a predetermined voltage in relation to the N-type well 2. Theelectrodes 15 and 17 are biased with the same voltage while theelectrode 16 is biased with a voltage of reverse polarity. The biasingof an electrode in relation to the N-type well 2 has the effect that,dependent on the sign of the bias, the charge carrier density in thearea underneath the electrode is either increased or decreased. In orderto increase the charge carrier density, the bias of the electrode has tobe inverse to the type of the charge carriers of the well 2. When thewell 2 is N-type, then the bias of the electrode has to be positive inrelation to the potential of the well 2. In order to reduce the chargecarrier density, the bias of the electrode has to be of the same type asthe charge carriers and of the well 2. When the well 2 is N-type, thenin this case the bias of the electrode has to be negative in relation tothe potential of the well 2.

It is also possible, instead of three electrodes 15, 16 and 17 toprovide only one single electrode, namely the electrode 16 between theinner contacts 5 and 6 or only the two electrodes 15 and 17 that areeach arranged between an inner and an outer contact. Furthermore, it ispossible with the example according to FIG. 4 to provide an additionalelectrode that is arranged between the contacts 4 and 12 or, with theexample according to FIG. 5, to provide two additional electrodes thatare arranged between the contacts 4 and 12 and between the contacts 7and 14. By selecting the size and sign of the bias applied to theindividual electrodes, the resistors R₁ to R₅ can be altered withincertain limits. Therefore, electronic voltage sources are provided thatare realised in the same semiconductor chip as the Hall element 1,whereby the biases to be applied to the individual electrodes aredetermined once in a calibration procedure so that the resistance bridgeformed by the resistors R₁ to R₅ is optimally balanced.

A further possibility of reducing or increasing the resistors R₁ to R₃with given position and size of the contacts 4-7 exists in increasing orreducing the charge carrier density by means of the local implantationof additional or fewer ions. This possibility is explained in moredetail based on FIG. 7. The contacts 4 to 7 are represented by areasthat are bordered with a broken line 18. With the formation of theN-type well 2, a mask 19 is used for the ion implantation that does nothave one single opening 20 corresponding to the size of the well 2 butan opening 20 that has local islands 21 that cover a part of the opening20 so that the doping of the N-type well 2 varies locally. Thedimensions of the islands 21 are selected so small that the areasseparated by the islands 21 connect to the N-type well 2 on thediffusion following the implantation. The doping of the well 2 in thearea between the two inner contacts 5 and 6 is therefore different tothe doping of the well 2 in the areas between an inner contact and anadjacent outer contact.

FIGS. 8 and 9 illustrate a further possibility of largely balancing theresistance bridge formed by the resistors R₁ to R₄, namely by theparallel connection of two Hall elements 1 and 1′ that are arrangedparallel to each other so that they measure the same component of themagnetic field. The directions of the currents flowing through the twoHall elements 1 and 1′ are presented symbolically by means of arrowsthat point from the contact where the current is supplied to the contactwhere the current is discharged. The contacts 4-7 of the first Hallelement 1 and the contacts 4′-7′ of the second Hall element 1′ are wiredin pairs via schematically presented conductors paths to 13. The wiringhas to fulfil two criteria that are described as follows. First of all,the Hall voltages of the two Hall elements 1 and 1′ produced by themagnetic field have to be equidirectional otherwise the magnetic fieldsensor does not “see” the magnetic field. When the two current contactsare connected by an arrow that indicates the direction of the current,then one voltage contact is always located on the left-hand side of thearrow and one voltage contact on the right-hand side of the arrow.Equidirectional now means that the two voltage contacts of the two Hallelements 1 and 1′ that lie on the left-hand side of the correspondingarrow have to be connected and that the two voltage contacts of the twoHall elements 1 and 1′ that lie on the right-hand side of thecorresponding arrow have to be connected. If the two Hall elements 1 and1′ were not wired, then with the first Hall element 1, one of the twovoltage contacts 5 and 7 would carry a higher potential than the othervoltage contact as the resistor R₄ is larger than the other resistorsR₁, R₂ and R₃. Equally, with the second Hall element 1′ one of the twovoltage contacts 4′ and 6′ would carry a higher potential than the othervoltage contact as here also the resistor R₄′ is larger than the otherresistors R₁′, R₂′ and R₃′. With the example in FIG. 8—with thedirection of the current presented in FIG. 8—the voltage contact 7 ofthe first Hall element 1 carries the higher potential than the voltagecontact 5. With the second Hall element 1′ the voltage contact 4′carries the higher potential than the voltage contact 6′. Secondly, thevoltage contacts 7, 5, 4′ and 6′ of the two Hall elements 1 and 1′ arenow to be wired in such a way that the voltage contact 7 of the firstHall element 1 that carries the higher potential is connected to thevoltage contact 6′ of the second Hall element 1′ that carries the lowerpotential. Because of this wiring, the currents flowing through the twoHall elements 1 and 1′ are distributed in such a way that, withvanishing magnetic field, the voltage applied between the voltagecontacts 7 and 5 of the first Hall element 1, the so-called offsetvoltage, is much lower than it would be without connection of the secondHall element 1′ in the way described. With the example presented in FIG.8, the contacts 4-7 of the first Hall element 1 and the contacts 4′-7′of the second Hall element 1′ are wired in pairs as follows: The contact4 with the contact 7′, the contact 5 with the contact 4′, the contact 6with the contact 5′ and the contact 7 with the contact 6′, whereby thecurrents in both Hall elements 1 and 1′ always flow from an innercontact to the not adjacent outer contact but in the opposite direction.

With the example presented in FIG. 9, the currents flow in the samedirection, with the first Hall element 1 from an inner contact to thenot adjacent outer contact, however with the second Hall element 1′ froman outer contact to the not adjacent inner contact. The contacts 4-7 ofthe first Hall element 1 and the contacts 4′-7′ of the second Hallelement 1′ are wired in pairs as follows: The contact 4 with the contact5′, the contact 5 with the contact 6′, the contact 6 with the contact 7′and the contact 7 with the contact 4′ so that the two criteria givenabove are fulfilled.

With the embodiments described up to now the symmetrical vertical Hallelement 1 is embedded in the N-type well 2 that has been produced in aP-type substrate by the implantation of ions and the subsequentdiffusion. Such a technology is generally designated as CMOS technology.However, instead of a CMOS technology, a bipolar technology can also beused with which the symmetrical vertical Hall element 1 is embedded inan insulated area in an epitactical layer. Such an insulated area canalso be designated as N-type well. While the N-type well produced withbipolar technology is homogeneously doped with impurity atoms, thedoping of the N-type well produced with CMOS technology is nothomogeneous.

1. A magnetic field sensor comprising a Hall element comprising a firstcontact, a second contact, a third contact and a fourth contact arrangedin this sequence along a straight line on a surface of a first well of afirst conductivity type that is embedded in a substrate of a secondconductivity type, said four contacts being two inner contacts and twoouter contacts, a first of said two outer contacts and a first of saidtwo inner contacts for supply and discharge of a current flowing throughthe first Hall element, wherein the first of said two outer contacts andthe first of said two inner contacts are not adjacent contacts, and asecond of said two outer contacts and a second of said two innercontacts for tapping a first Hall voltage, wherein the two innercontacts are the same width and wherein the two outer contacts are thesame width, wherein a distance between the first contact and the secondcontact is equal to a distance between the third contact and the fourthcontact, wherein a distance between the second contact and the thirdcontact is selected such that approximately R₁=R₂=R₃ wherein R₁ denotesa resistance prevailing between the first contact and the second contactR₂ denotes a resistance prevailing between the second contact and thethird contact and R₃ denotes a resistance prevailing between the thirdcontact and the fourth contact, and wherein the two outer contacts areconnected via an additionally resistor having a resistance R₅ that isselected such that approximately R₁=R₂=R₃=R₄||R₅ wherein R₄ denotes aresistance prevailing between the first contact and the fourth contact.2. The magnetic field sensor according to claim 1, wherein saidadditional resistor is formed by an additional well of the firstconductivity type embedded in said substrate.
 3. The magnetic fieldsensor according to claim 1, wherein a fifth contact is arranged in thewell of the Hall element next to the first contact of the Hall elementon a side facing an adjacent edge of the well and wherein the fifthcontact is connected to the fourth contact by a conductor path, so thatsaid additional resistor is formed by a resistance prevailing betweenthe first contact and the fifth contact.
 4. The magnetic field sensoraccording to claim 1, wherein a fifth contact is arranged in the sell ofthe Hall element next to the first contact of the arranged in the wellof the Hall element next to the fourth contact of the Hall element on aside facing an adjacent edge of the well and wherein the fifth contactis connected to the sixth contact by a conductor path, so that saidadditional resistor is formed by a resistance prevailing between thefirst contact and the fifth contact and a resistance prevailing betweenthe sixth contact and the fourth contact.
 5. The magnetic field sensoraccording to claim 1, wherein at least one electrode electricallyinsulated from the well is arranged between two contacts.
 6. Themagnetic field sensor according to claim 2, wherein at least oneelectrode electrically insulated from the well is arranged between twocontacts.
 7. The magnetic field sensor according to claim 3, wherein atleast one electrode electrically insulated from the well is arrangedbetween two contacts.
 8. The magnetic field sensor according to claim 4,wherein at least one electrode electrically insulated from the well isarranged between two contacts.
 9. The magnetic field sensor according toclaim 1, wherein a doping of the well in an area between the two innercontacts is different to a doping of the well in the areas between aninner contact and an outer contact.
 10. The magnetic field sensoraccording to claim 2, wherein a doping of the well in an area betweenthe two inner contacts is different to a doping of the well in the areabetween an inner contact and an outer contact.
 11. The magnetic fieldsensor according to claim 3, wherein a doping of the well in an areabetween the two inner contacts is different to a doping of the well inthe area between an inner contact and an outer contact.
 12. The magneticfield sensor according to claim 4, wherein a doping of the well in areabetween the two inner contacts is different to a doping of the well inthe areas between an inner contact and an outer contact.
 13. A magneticfield sensor comprising a first Hall element comprising a first contact,a second contact, a third contact and a fourth contact arranged in thissequence along a first straight line on a surface of a first well of afirst conductivity type that is embedded in a substrate of a secondconductivity type, said four contacts being two inner contacts and twoouter contact, a first of said two outer contacts and a first of saidtwo inner contacts for supply and discharged of a current flowingthrough the first Hall element, wherein the first of said two outercontacts and the first of said two inner contacts are not adjacentcontacts, and a second of said two outer contacts and a second of saidtwo inner contacts for tapping a first Hall voltage, wherein the twoinner contacts are the same width and wherein the two outer contacts arethe same width, wherein a distance between the first contact and thesecond contact is equal to a distance between the third contact and thefourth contact, a second Hall element comprising a first contact, asecond contact, a third contact and a fourth contact arranged in thissequence along a second straight line on a surface of a second well ofthe first conductivity type that is embedded in the substrate, said fourcontacts being two inner contacts and two outer contacts, a first ofsaid two outer contacts and a first of said two inner contacts forsupply and discharge of a current flowing through the second Hallelement, wherein the first of said two outer contacts and the first ofsaid two inner contacts are not adjacent contacts, and a second of saidtwo outer contacts and a second of said two inner contacts for tapping asecond Hall voltage, wherein the two inner contacts are the same widthand wherein the two outer contacts are the same width, wherein adistance between the first contact and the second contact is equal to adistance between the third contact and the fourth contact, wherein thefirst and second straight line run in parallel, an wherein either thefirst contact of the first Hall element is connected with the fourthcontact of the second Hall element, the second contact of the first Hallelement is connected with the first contact of the second Hall element,the third contact of the first Hall element is connected with the secondcontact of the second Hall element and the fourth contact of the firstHall element is connected with the third contact of the second Hallelement or the first contact of the first Hall element is connected withthe second contact of the second Hall element, the second contact of thefirst Hall element is connected with the third contact of the secondHall element, the third contact of the first Hall element is connectedwith the fourth contact of the second Hall element and the fourthcontact of the first Hall element is connected with the first contact ofthe second Hall element.
 14. The magnetic field sensor according toclaim 13, wherein a distance between the second contact and the thirdcontact of the first Hall element is selected such that approximatelyR₁=R₂=R₃ wherein R₁ denotes a resistance prevailing between the firstcontact and the second contact of the first Hall element, R₂ denotes aresistance prevailing between the second contact and the third contactof the first Hall element and R₃ denotes a resistance prevailing betweenthe third contact and the fourth contact of the first Hall element,wherein the two outer contacts of the first Hall element are connectedvia a first additional resistor having a resistance R₅ that is selectedsuch that approximately R₁=R₂=R₃=R₄||R₅ wherein R₄ denotes a resistanceprevailing between the first contact and the fourth contact of the firstHall element, wherein a distance between the second contact and thethird contact of the second Hall element is selected such thatapproximately R₁′=R₂′=R₃′ wherein R₁′ denotes a resistance prevailingbetween the first contact and the second contact of the second Hallelement, R₂′ denotes a resistance prevailing between the second contactand the third contact of the second Hall element and R₃′ denotes aresistance prevailing between the third contact and the fourth contactof the second Hall element, and wherein the two outer contacts of thesecond Hall element are connected via a second additional resistorhaving a resistance R₅′ that is selected such that approximatelyR₁′=R₂′=R₃=′R₄′||R₅′ wherein R₄′ denotes a resistance prevailing betweenthe first contact and the fourth contact of the second Hall element.